Method for detecting a vehicle traffic status and system for detecting said traffic status

ABSTRACT

From a body located at a distance above the surface of the earth, an image is recorded of a region that is located underneath the body on or above the surface of the earth and that has a diameter of at least one kilometer. The recorded image is fully geocoded and comprises a grid dimension small enough that vehicle densities located in the region can be recognized. The recorded image is evaluated with respect to these vehicle densities and the spatial allocation thereof to the associated roadways. The method is used for acquisition of the state of street traffic over a large area.

BACKGROUND OF THE INVENTION

The invention relates to a method for acquiring a traffic state ofvehicles and to an apparatus for acquiring such a traffic state.

For the goal-oriented use of traffic guidance systems, a reasonableadjustment of the switching phases of light signal apparatuses, and fora determination of roadway construction measures that is in accordancewith traffic conditions, a computer-supported simulation and forecastingof traffic flow that is as comprehensive as possible is necessary. Inorder to match the programs used for this purpose with actualconditions, comprehensive information about the actual state of trafficin the areas under consideration must however be present. In denselypopulated areas in particular, it is hereby not sufficient to acquireonly individual roadways with regard to traffic flows; rather, an imageof the traffic situation that is as complete as possible, includingpossible alternative routes, detours, etc., is required.

The acquisition of the actual traffic state that is important for theoptimization of the traffic flow has up to now been carried out viameasurement installations at the infrastructure, for example in streettraffic via measurement loops in the roadway or by means of trafficcounts that are highly personnel-intensive. However, these techniquesare very strongly locally limited, and do not allow an overall view. Inaddition, their diagnostic effectiveness may be low, according towhether the measurement location has been chosen correctly orincorrectly. In addition, measurement apparatuses at the infrastructureare stationary and are connected with significant costs both forinstallation and for maintenance. For these reasons, as a rule thesemeasurement methods are limited to few locations.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method for acquisition ofa traffic state of vehicles over a large area.

According to the method of the present invention for acquiring a trafficstate of vehicles, from a body located at a distance above a surface ofthe earth, recording an image of the region located underneath the bodyat or above the surface of the earth and that has a lateral diameter ofat least one kilometer. The image is recorded with a grid dimension thatis small enough that densities of at least one particular type ofvehicle located in the region can be recognized up to a predeterminedmaximum density. The recorded image is evaluated with regard to at leastone density for at least one type of vehicle.

According to this solution, from a body located at a distance above thesurface of the earth an image is recorded of a region that is locatedunderneath the body on and/or above the surface of the earth and thathas a lateral diameter of at least one kilometer, said image beingrecorded with a grid dimension that is small enough so that densities ofat least one of a particular type of vehicle located in the region canbe recognized, up to a predetermined maximum density, and the recordedimage is evaluated with regard to at least one density at least of theone type of vehicle.

As a body, a geosatellite orbiting the earth is preferably used. Due toits great distance from the surface of the earth—on the order of 100kilometers—such a satellite has the advantage that particularly largeregions, of for example 50×100 kilometers surface area, and in any casea region having a diameter on the order of magnitude of 10 kilometers,can be monitored.

In this way, traffic of every type and/or type of vehicle, includingland vehicles not bound by rail, for example all types of passengervehicle and/or truck, rail-bound vehicles, for example all types ofrailway trains for passenger or freight traffic, water vehicles, forexample all types of passenger and freight ships, both at sea and oninland waterways, as well as aircraft, for example all types ofpassenger and freight airplane, can advantageously be monitored rapidlyand reliably over a larger area than was previously known or possible.In particular, vehicles can advantageously be monitored, in particularsimultaneously, both in a manner separated according to the speciesand/or type of vehicle and also in a manner disregarding the speciesand/or type of vehicle.

With a single satellite orbiting the earth, every 2 to 4 days individualimages and chronological sequences of images of the same region can beproduced.

As a body, a geostationary geosatellite can also be used, whichadvantageously enables a constant monitoring of traffic in a region ofalmost the size of an entire hemisphere, for example the ship traffic inthe Atlantic or Pacific.

From a geosatellite, images of the large regions can be producedoptically with sufficiently high resolution, but this type of recordingdepends on the time of day and on the weather. If in contrast radarradiation is used for recording the images, the images canadvantageously be recorded at all times of day and in all types ofweather. However, a radar radiation and a radar system must be used thatenable images having a sufficiently small grid dimension, correspondingto a sufficiently high resolution. A dimension of two meters is regardedas the lower limit of the grid dimension, at least in relation to streettraffic, in order to enable differentiation of lane positions. Densitiesof street vehicles can thereby be unambiguously recognized andallocated, because the vehicles have different degrees of reflectionthan do the roadways, and corresponding differences of brightnesstherefore exist in the recorded images.

Instead of a body in the form of a satellite, a body in the form of anaircraft can also be used in the inventive method, whereby as anaircraft an airplane can primarily be used, but for example a balloon orthe like is also possible. From the airplane, images of regions of awidth of five to seven kilometers can for example be realized, and inany case regions comprising a diameter of the order of magnitude of 1kilometer.

In order to remain independent of the time of day and the weatherconditions in this case as well, it is again recommended that the imagesbe recorded not optically but rather using radar, advantageously SAR.Here as well, in relation to street traffic two meters is regarded asthe lower limit of the grid dimension.

In any case, it is thus advantageous to record an image by means of aradiation of radar.

If the images are recorded with the aid of interferometry and/or theDoppler effect, it is advantageously possible to acquire velocities ofthe vehicles in addition to vehicle densities.

The inventive method is particularly advantageous for the acquisitionover a large area of a state of street traffic and for monitoring andguiding the street traffic in large cities, but is also suitable for usein smaller cities and/or rural areas, but is not limited to this, butrather can, as already mentioned, in principle also be used formonitoring the movement of railway trains, ships and/or aircraft,particularly in harbor areas and airport areas.

An advantage of the inventive method can be seen in its suitability forthe use of georeferencing, which enables a rapid and precise allocationbetween a point in the region and the corresponding point on therecorded image of this region. In an advantageous realization of theinventive method, a spatial allocation is created between a vehicledensity recognized in an image of the region and a roadway of theregion, using georeferencing, which, in particular given images recordedfrom artificial geosatellites, enables a spatial allocation of vehicledensities to the respective roadways.

A monitoring of modifications of the traffic conditions canadvantageously be achieved if after recording an image of the region atleast one additional image of the same region is recorded and islikewise evaluated with regard to vehicle densities found in the region,and if at least two recorded images are compared with one another. Inthis way, a direct optimization, for example in relation to streettraffic, of the control algorithms of traffic guidance systems andtraffic light phases can advantageously be realized by means of acomparison before and after the optimization technique. In addition,intended modifications by means of street construction techniques canadvantageously be monitored, and existing simulation programs can beprecisely matched.

In this case, it is particularly advantageous if at least a sequence oftwo images of the region is produced by individual momentary exposuresthat succeed one another chronologically within one hour. Such asequence of images can advantageously be used for the acquisition of thetraffic state and the chronological modification thereof in real time,or can also be used at a later time, for example in reference to thestreet traffic for the production of current traffic conditions fortraffic information, the direct controlling of traffic guidance systems,and for the adjustment of traffic flow simulations, whereby in additiona direct optimization of the control algorithms of traffic guidancesystems and traffic light phases can be realized by a before/aftercomparison. The evaluation of the exposures can take place manually, orelse, in a shorter time and with a lower personnel expense, by machine,if a system is available for the recognition of vehicle density in theimages and for the spatial allocation of the vehicle densities to therespective roadways.

The actual evaluation of the exposures can take place already in thebody, for example on board the satellite or aircraft. An advantageousarrangement, suitable for this purpose, for acquiring a traffic state iswhen the body, located at a distance above the surface of the earth, inparticular a geosatellite orbiting the earth, is a geostationarygeosatellite or is an aircraft.

According to an advantageous construction of the inventive arrangement,the evaluation unit converts a particular information content of arecorded image into coded data signals.

The evaluation unit advantageously produces georeferenced coded datasignals, with the aid of which a reference to land maps for roadways tobe examined, and thereby a spatial allocation of vehicle densities torespective roadways, is produced.

From the coded data signals, an item of information concerning a trafficstate in the relevant region is obtained, preferably using a processingunit for a processing of the data signals in order to obtain an item ofinformation concerning a traffic state in the region. The processingunit is preferably located on the surface of the earth, in particular instationary fashion.

An item of information concerning a traffic state in the region issupplied for a further use, preferably in the form of data that arerelevant only for this use, and preferably in a use unit provided forthis use. For various uses concerning a traffic state, different useunits can be used, which are preferably located on the surface of theearth, in particular in stationary fashion.

In the following specification, the invention is explained in moredetail in exemplary fashion on the basis of the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, in a perspective view, a body located at a distance fromthe surface of the earth, from which at least one image of a region ofthe surface of the earth is recorded;

FIG. 2 shows a detail of an image of a region of the surface of theearth recorded photographically from an artificial satellite orbitingthe earth;

FIG. 3 shows a detail of an image of the region of the surface of theearth recorded by an artificial satellite orbiting the earth by means ofradar radiation;

FIG. 4 shows a detail of an image of the region of the surface of theearth recorded photographically from an airplane in flight;

FIG. 5 shows a detail of an image of the region of the surface of theearth recorded by means of radar from an airplane in flight; and

FIG. 6 shows an exemplary arrangement for the acquisition of a trafficstate.

The figures are schematic and are not to scale.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to FIG. 1, a body 2 from which an image of a region 10 isrecorded is located at a distance a above the surface of the earth 1,said region being located below the body 2 or in the airspace over thesurface of the earth 1. The body 2 can be a geosatellite or an aircraft.The surface of the earth 1 should be understood as not only the surfaceof solid land, but also the water surface of the earth.

Let it be assumed that the body 2 is an artificial satellite that orbitsthe earth at a distance a standard for such satellites, on the order ofmagnitude of 100 kilometers.

From this satellite 2, an image of a region 10—for example,strip-shaped—having a length l of approximately 100 kilometers and awidth b of approximately 50 kilometers is recorded. In FIG. 1, thecurvature of the surface of the earth 1 is ignored.

The image is to be recorded using a radiation 5 that ensures that in theimage a grid dimension is small enough that densities at least of aparticular type of vehicle located in the region 10 can be recognized,up to a predetermined maximum density.

In FIG. 2, a detail 11′ of an image 3, recorded from the satellite 2, ofthe region 10 is shown, it being assumed that this image 3 of the region10 is produced photographically, that is, using an optical radiation 5,and the image detail 11′ corresponds to the relatively small section 11of the region 10 in FIG. 1. The optical radiation 5 can be ultraviolet,visible, and/or infrared light.

In this photographically recorded image 3 of the region 10, andtherefore also in the image detail 11′, there is a grid dimension thatis determined by the wavelengths of the optical radiation 5 that is usedand the resolution capacity of an optical recording apparatus. In thiscase, grid dimensions well under 0.5 meters are possible, so thatobjects such as individual vehicles are imaged with fairly sharpcontours.

For example, let the region 10 be a part of the surface of the earth 1covered with a network of streets and highways, and let a highway 110,traveled by vehicles, run through the segment 11 of the region 10. Otherrecognizable structures of the landscape in the section 11 of the region10, such as for example trees and bushes, houses, additional streets,rivers, bridges, etc., are omitted in the image detail 11′ according toFIG. 2 for the sake of simplicity.

The highway 110 comprises for example of two roadways 112 and 113,separated from one another by a green strip 111, of which each forexample comprises two lanes 112 ₁, 112 ₂, or, respectively, 113 ₁, 113₂, each two being for example separated by a dividing line 112 ₃ or,respectively, 113 ₃.

Let the roadway 112 be provided for the direction of travel 114 frombottom to top, and let the roadway 113 be provided for the direction oftravel 115 from top to bottom.

Vehicles located on the roadways 112 and 113 standardly includepassenger vehicles, buses, and trucks with and without trailers. Forexample, in FIG. 2 a single truck or bus is present that is located inlane 113, and is designated 4′, while all other vehicles on the highway110 are assumed to be passenger vehicles, of which each is alreadyvisually distinguished merely by its shorter length e in comparison tothe length e′ of the truck or bus. Some individual passenger vehiclesare designated 4, as representative of the others. A total of thirteenpassenger vehicles are located on the segment of the highway 110 in theimage detail 11′.

Assuming right-hand traffic, for example, three passenger vehicles 4 arelined up closely to one another behind the truck or bus 4′, for exampleon the right lane 113 ₁ of the roadway 113, since for example the truckor bus 4′ is at this moment being overtaken by a faster-travelingpassenger vehicle 4 on the left lane 113 ₂, and the three passengervehicles 4 must wait behind the truck or bus 4′ until the left lane 113₂ is free again.

The density of vehicles on a lane is determined by the distance dbetween vehicles succeeding one another in the direction of travel (oralso opposite the direction of travel). The greater the distance dbetween successive vehicles, the lower the density of the vehicles.

In the example according to FIG. 2, in the group of vehicles 40comprising the truck or bus 4′ and the three passenger vehicles 4 linedup close to one another therebehind, a maximum density of the vehiclesis present, since in this group 40 the distance d0 between thesuccessive vehicles 4′ and 4 is visibly minimal in comparison to thedistances d existing between the successive vehicles 4 not belonging tothe group 40.

The absolute maximum density of vehicles on a lane is given when thevehicles bump into one another with no gap, that is, when d is equal tozero. In street traffic, the absolute maximum density, apart fromsingular cases, does not occur, because the vehicle drivers strivealways to maintain a minimum distance d greater than 0.

The grid dimension r determines in general a maximum density of thevehicles, above which densities of the vehicles, determined by distances0≦d≦r, cannot be distinguished from one another and therefore cannot berecognized, because the vehicles can no longer be kept separate from oneanother. In contrast, vehicles with distances d>r can be kept separatefrom one another, and densities of these vehicles, determined bydistances d, which area whole-number multiple of the grid dimension r,can be distinguished from one another and thereby recognized.

If the maximum density d=r of the vehicles is present, with the aid ofthe grid dimension r a lower limit is indicated for the number ofvehicles contained in the continuously appearing queue of vehicles thatcannot be distinguished.

In relation to FIG. 2, it is for example assumed that the photographicoptical recording apparatus used has a resolution capacity high enoughthat the grid dimension r is approximately 0.1 meters, and apredetermined maximum density of the vehicles is thus essentiallyequivalent to the absolute maximum density, because in relation to thesize of vehicles, 0.1 meters is negligibly small.

In relation to FIG. 3, it is assumed that the image detail 11′ does notoriginate from a photographically recorded image of the region 10, butrather from an image 3 of the region 10 recorded using a radar radiation5.

The image detail 11′ according to FIG. 3 shows, as does the image detail11′ according to FIG. 2, only the highway 110 and the vehicles locatedthereon, but for the sake of simplicity does not show any furtherdetails of the landscape.

Let it be further assumed that the image 3 recorded using the radarradiation 5 was recorded from the satellite 2 at the same time as wasthe photographic image 3, so that in the image detail 11′ according toFIG. 3 the vehicles 4′ and 4 are in the same traffic state on thehighway 110 as in the image detail 11′ according to FIG. 2.

In comparison with the photographic image detail 11′ according to FIG.2, the image recorded using the radar radiation 5, and thereby the imagesegment 11′ according to FIG. 3, comprises an unequally larger griddimension r>0.5 m, and thereby an unequally weaker geometric resolution.The grid dimension r is indicated in FIG. 3.

On the basis of this comparatively coarse grid dimension r, in the imagedetail 11′ according to FIG. 3, in contrast to the image detail 11′according to FIG. 2, the roadways 112 and 113, as well as the vehicles4′ and 4 on the roadways 112 and 113, do not have sharp boundaries. Thedividing lines 112 ₃ and 113 ₃ also can no longer be recognized. Theprimary cause of the coarse grid dimension r is to be found in thelarger wavelengths of the radar radiation 5, which are unequal to theoptical wavelengths.

What is more, each vehicle on a roadway 112 and/or 113 appears as adiffuse spot, which is advantageously clearly distinguished in relationto the background formed by this lane. The reason for this is to befound in the advantageous circumstance that a lane, or in general thesurface of the earth, has a significantly different reflective capacityfor radar radiation 5 than does a vehicle located thereon.

In the image recorded using the radar radiation 5, and thus in the imagedetail 11′, objects and distances that are smaller than the griddimension r are no longer perceived.

In the method here specified, a grid dimension r that is essentiallyequal to two meters is advantageously sufficient.

Given this grid dimension r=2 meters, small, medium, and high densitiesof vehicles, corresponding to moderate, medium, and heavy traffic, canbe recognized and distinguished from one another on the image 3 of theregion 10 to the extent that the vehicles and distances between thesuccessive vehicles can essentially be individually recognized, and,given moderate, medium, and heavy traffic, these distances are onaverage respectively clearly distinguished from one another.

On the other hand, given this grid dimension r=2 meters, slow traffic orstalled traffic can be recognized in that the vehicles on the image 3are to a large extent no longer separated from one another, but ratherare essentially seen as a continuous line, because the distances betweensuccessive vehicles are close to two meters. In particular, such a linehaving a length of one or more kilometers is a certain indicator of atraffic jam, if in a comparison of two or more images 3, recorded atdifferent times, no movement of at least one end can be recognized, andis a certain indicator of slow traffic if such a comparison reveals amovement of the line.

In FIGS. 2 and 3, as an example it is assumed (though somewhatunrealistically) that the distance d0 between the successive fourvehicles 4′ and 4 of the group of vehicles 40 is close to or equal totwo meters. This group 40 accordingly appears as a continuous line ofvehicles.

The lengths of passenger vehicles differ from one another significantlyby less than two meters, and, given a distance d of more than twometers, can be recognized as such with the method here specified. Thelengths of trucks and buses of the same weight class also differ fromone another by significantly less than two meters, but in many casesdiffer from passenger vehicles by more than two meters. In these cases,with the method here specified trucks and buses of the same weight classcan be recognized as such and can be distinguished from passengervehicles, at least in the case of flowing traffic and given a distance dof more than two meters. Different species and/or types of vehicles canthus be kept separate, and the densities thereof can also be determinedindividually using the radar radiation, which produces a grid dimensionr of two meters.

With reference to FIGS. 4 and 5, it is assumed that the body 2 accordingto FIG. 1 is an airplane flying at a distance a of 8 to 10 kilometersfrom the surface of the earth 1, from which an image of a region 10, forexample which is strip-shaped, of the surface of the earth 1 isrecorded, whereby the region 10 has a length l of approximately 9kilometers and a width b of approximately 5 to 7 kilometers.

In FIG. 4, an image detail 11′ of the image 3, recorded from theairplane 2, of the region 10 is shown, whereby it is assumed that thisimage 3 is produced photographically and the image detail 11′corresponds to the relatively small section 11 of the region 10 in FIG.1.

For example, assume now that the region 10 is the street traffic networkof a city, of which the segment 11 of the region 10 shows anintersection 120 traveled by vehicles. Other recognizable structures ofthe city landscape in the segment 11 of the region 10, such as forexample trees and bushes, houses, additional streets, rivers, bridges,etc., are omitted in the image detail 11′ according to FIG. 4 for thesake of simplicity.

In the intersection 120, for example, two streets 121 and 122 cross.Each street 121 and 122 has for example two lanes 121 ₁, 121 ₂, or,respectively, 122 ₁ or 122 ₂, separated from one another by a dividingline 121 ₃ or, respectively, 122 ₃.

In the street 121, the lane 121 ₁ is provided for a direction of travel121 ₄, and the lane 121 ₂ is provided for the direction of travel 121 ₅opposed to a direction of travel 121 ₄. In the street 122, the lane 122₁ is provided for a direction of travel 122 ₄, and the lane 122 ₂ isprovided for the direction of travel 122 ₅ opposed to a direction oftravel 122 ₄.

At the intersection 120, a traffic light installation (not shown) ispresent that at the moment at which the image was recorded was forexample switched such that the street 122 has the red, and thevehicles—made up without exception of passenger vehicles 4—on both lanes122 ₁ and 122 ₂ of this street 122 must wait in front of theintersection 120 while the vehicles—for example likewise made up withoutexception of passenger vehicles 4—on the two lanes 121 ₁ and 121 ₂ ofthe street 121 have the green and are permitted to cross theintersection 120.

Accordingly, on the street 122 a group 41 consisting of a plurality—forexample four—passenger vehicles 4 is lined up on the street 122 in frontof the intersection 120 on the lane 122 ₁, and on the lane 122 ₂ a group42 consisting of a plurality—for example five—passenger vehicles 4 is solined up.

In reference to FIG. 5, it is assumed that the image detail 11′ does notoriginate from a photographically recorded image 3 of the region 10, butrather from an image 3 of the region 10 recorded using a radar radiation5.

The image detail 11′ according to FIG. 5 shows, as does the image detail11′ according to FIG. 4, only the intersection 120 with the streets 121and 122 and the vehicles located thereon, and for the sake of simplicityshows no further details of the city landscape.

In comparison with the photographically recorded image 3, and thus withthe image detail 11′ according to FIG. 4, the image 3 recorded with theradar radiation 5, and thus the image detail 11′ according to FIG. 5,comprises the unequally larger grid dimension r, of for example twometers, and thus an unequally weaker geometric resolution.

Let it also be assumed here that the image 3 recorded using the radarradiation 5 was recorded from the airplane 2 at the same time as was thephotographic image 3, so that in the image detail 11′ according to FIG.5 the vehicles 4 are in the same traffic state as in the image detail11′ according to FIG. 4, on the intersecting streets 121 and 122.

On the basis of this comparatively coarse grid measure r, in contrast tothe image detail 11′ according to FIG. 4, in the image detail 11′according to FIG. 5 the streets 121 do and 122 as well as the vehicles 4on the streets 121 and 122 are respectively not sharply delimited. Thedividing lines 121 ₃ or, respectively, 122 ₃ also can no longer berecognized.

In this case as well, each vehicle 4 appears on the streets 121 and 122as a diffuse spot that advantageously stands out clearly against thebackground given by these streets. The cause for this is again thefavorable circumstance that a roadway, or in general the ground, has asignificantly different reflection factor for the radar radiation 5 thandoes a vehicle located thereon.

Let it be assumed that in each group 41 and 42 of vehicles 4 on thestreet 122 each distance d0 between successive vehicles 4 is smallerthan the grid dimension r, while on each lane 121 ₁ and 122 ₂ and on thestreet 121 each distance d between successive vehicles 4 is greater thanthe grid dimension r. Accordingly, each of these groups 41 and 42appears as a continuous line of vehicles, while the vehicles 4 on thestreet 121 can be recognized individually.

The streets 121 and 122 according to FIGS. 4 and 5 are each a streetwith two-way traffic, that is, a street having one lane intended for onedirection of travel and one lane intended for the opposite direction oftravel, whereby these two lanes are separated from one another only by adividing line, or at least run next to one another with a very smallspacing. Given such a street, it is important to be able to allocate thevehicles to the individual lanes, and thereby directions of travel, onan image 3 of the region 10. This holds in particular in the case ofslow traffic or stalled traffic. In this case, it is particularlyimportant to allocate a line of vehicles indicating such a traffic stateon the image 3 to the correct direction of travel, because, for example,it would be fatal to signal to the traffic participants a traffic jam inthe wrong direction. A grid dimension r of two meters is advantageouslysufficient for an unambiguous and reliable allocation of the vehicles tothe correct lane and thereby the correct direction of travel.

Moreover, given this grid dimension r=2 m, it is advantageously alsopossible to recognize a parking situation on streets and places, thatis, to determine to what extent streets and places are occupied byparking vehicles.

Besides the advantages presented above, the relatively coarse griddimension r of two meters has the advantage that it is easy to realizeusing the advantageous radar radiation 5. However, the invention is notlimited to this coarse grid dimension; rather, smaller, but also larger,grid dimensions can be used, according to the advantages to be gained atthe moment according to the circumstances of the individual case. Forexample, a smaller grid dimension is to be used if it is important torecognize details that are smaller than two meters.

Regardless of whether an image of a region 10 is recorded using radarradiation 5 from a satellite 2 or from an aircraft 2, after such arecording of such an image of the region 10 it is useful to record atleast one additional image of the region 10, and likewise to evaluatethis image with regard to the at least one density of the at least oneparticular type of vehicle 4 located in the region 10, and thereby tocompare at least two images recorded in this way with one another.Preferably, the sequence of at least two images of the region 10 isproduced by chronologically successive individual momentary exposures.

In the arrangement shown in FIG. 6 for acquiring a traffic state, animage recording unit 20 is present that is attached to a body 2 locatedat a distance a above the surface of the earth 1. This image recordingunit 20 is used for an exposure of an image 3 of a region 10 that islocated underneath the body 2 on and/or above the surface of the earth1, and that has a lateral diameter of at least one kilometer.

The image is recorded with a grid dimension r that is small enough thatdensities at least of a particular type of vehicle located in the region10, for example passenger vehicles 4 or buses or trucks 4′ in FIGS. 2and 3, can be recognized up to the maximum density determined by thegrid dimension r.

Moreover, an evaluation unit 21 is present at the body 2 for anevaluation of the recorded image 3 with respect to at least one densityof the at least one type of vehicle.

As already mentioned, the grid dimension r should be small enough sothat on the image of the region 10 a spatial allocation can berecognized between at least one density of at least one type of vehicle,for example of the vehicles 4 or 4′, and at least one roadway 110, 121,122, provided for this type of vehicle 4, of the region 10. A griddimension r of two meters is sufficient for this.

The evaluation unit 21 is for example fashioned such that it converts aparticular information content of a recorded image 3 into coded datasignals 22.

The image recording unit 20 and evaluation means 21 can be realized bythe fully geocoded interferometric radar with syntheticaperture—developed for ground exposures for purposes other than theacquisition of a traffic state—known from the TRANS catalog of MSTAerospace GmbH, Cologne, Federal Republic of Germany, which provides noteachings or indications in relation to the present invention. In an expost facto view from the point of view of the completed invention, thissystem is particularly suitable in particular for the acquisition over alarge area of a state of street traffic, be it via geosatellite or viaaircraft.

The coded data signals 22 produced by the evaluation unit 21 aretransmitted to a processing unit 30 that processes—for example incomputer-supported fashion—the data signals 22 in order to obtain anitem of information concerning a traffic state in the region 10. Theprocessing unit 30 is preferably housed in a ground station on thesurface of the earth 1. The transmission of the coded data signals 22are preferably transmitted in the form of electromagnetic waves from thebody 2 through open space to the ground station.

The information obtained in the processing unit 30 from the data signals22 concerning a traffic state in the region 10 can be supplied, viavarious transmission paths or information channels, to one or moredifferent use unit for the use of such an item of information. A useunit can for example be a radio transmitter 40 via which the trafficparticipants can be informed via radio about the traffic conditions inthe region 10, a comparison unit 50 that by means of before/aftercomparisons produces for example diagnoses concerning the development oftraffic in the region 10, or many other things. For example, the unit 50can forward its diagnoses to a central traffic guidance station 60,which can, with the aid thereof, control the flow of traffic on thestreets, for example via variable display unit 70 that indicate targetspeeds to the traffic participants.

Images 3 of one and the same region 10 that has been recorded fromdifferent bodies 2, for example from a satellite and from an airplane,can also be evaluated and/or compared with one another, in particulareven if these images have grid dimensions that differ from one another.

Although modifications and changes may be suggested by those skilled inthe art, it is the intention of the inventors to embody within thepatent warranted hereon all changes and modifications as reasonably andproperly come within the scope of their contribution to the art.

We claim:
 1. A method for acquiring a traffic state of vehicles,comprising the steps of: from a body located at a distance above asurface of the earth, generating an image of a region located underneaththe body at or above the surface of the earth and that has a lateraldiameter of at least one kilometer; recording said image with aresolution that is small enough so that a density of at least oneparticular vehicle type located in the region is recognized up to apredetermined maximum density; and evaluating the recorded image withregard to at least one density for at least one type of vehicle.
 2. Themethod according to claim 1 wherein a geosatellite orbiting the earth isused as the body.
 3. The method according to claim 1 whereby the imageof the region having a diameter on the order of magnitude of at least 10kilometers is recorded.
 4. The method according to claim 1 whereby ageostationary geosatellite is used as the body.
 5. The method accordingto claim 1 wherein an aircraft is used as the body.
 6. The methodaccording to claim 5 wherein the image recorded of the region has adiameter on the order of magnitude of one kilometer.
 7. The methodaccording to claim 1 wherein the image is recorded using a radarradiation.
 8. The method according to claim 1 wherein the image isrecorded with the use of interferometry.
 9. The method according toclaim 1 wherein the image is recorded with use of Doppler effect. 10.The method according to claim 1 wherein a spatial allocation is producedby means of georeferencing between a density recognized in the image ofthe region of vehicles, and a roadway of the region.
 11. The methodaccording to claim 1 wherein after the recording of the image of theregion, at least one additional image of the region is recorded, and islikewise evaluated with respect to the at least one density of the atleast one particular type of vehicle located in the region, and wherebyat least two images recorded in this way are compared with one another.12. The method according to claim 11 wherein at least one sequence oftwo images of the region is produced by individual momentary exposuressucceeding one another chronologically within one hour.
 13. The methodaccording to claim 1, further comprising the step of converting aparticular information content of the recorded image into coded datasignals.
 14. The method according to claim 13, wherein the coded signalsare georeferenced coded signals.
 15. The method according to claim 14,further comprising the step of processing the data signals to obtain anitem of information concerning a traffic state in the region.
 16. Themethod according to claim 15, further comprising the step of supplyingthe obtained item of information to a use unit.
 17. A method ofdetermining a traffic state of vehicles, comprising the steps of:selecting a resolution for an image-producing beam so that separatevehicles whose traffic state is to be determined cannot be distinguishedin an image produced by the image-producing beam when a spacing betweenthe vehicles is less than or equal to the resolution; radiating theimage-producing beam having the selected resolution from a body locatedat a distance above a surface of a region in which the state of trafficis to be determined, the region having a lateral diameter of at leastone kilometer; recording the image produced by the image-producing beam,wherein first vehicles spaced apart more than the resolution areseparately distinguishable in the recorded image and wherein groups ofplural second vehicles spaced apart less than or equal to the resolutionform continuous lines in the recorded image; and evaluating a density ofvehicles in the recorded image based on occurrences of the continuouslines.
 18. The method according to claim 17, further comprising thesteps of: recording another image in the region; evaluating a density ofvehicles in the another recorded image; and comparing the recorded andthe another recorded images to determine changes in the state oftraffic.
 19. The method according to claim 18, wherein in said recordinganother image step, the image and the another image are recordedchronologically within one hour.
 20. The method according to claim 17,further comprising the step of controlling a traffic guidance systembased on the compared images.